Screwdown control system for reversing mill



July 17, 1962 w. ROBERTS 3,044,330

SCREWDOWN CONTROL SYSTEM FOR REVERSING MILL Filed-Aug. 11, 1959 Digital voltmeter INVENTOR WILL/AM L. ROBERTS Alla/nay United States Patent 3,044,330 SCREWDOWN CONTROL SYSTEM FOR REVERSING MILL William L. Roberts, Murrysville, Pa., assignor to United States Steel Corporation, a corporation of New Jersey Filed Aug. 11, 1959, Ser. No. 833,014 4 Claims. (Cl. 80-56) This invention relates to a system for automatically controlling the screwdowns of a rolling mill in order to effect the maximum reduction possible, at the existing temperature of a workpiece, without overloading the mill.

In the primary rolling of steel, i.e., in blooming or slabbing mills, adherence to an arbitrary reduction schedule results in overloading the mill if the ingot being rolled is below proper temperature or inetlicient use of the mill capacity if the temperature is above the usual tempera- 'ture for rolling. It is accordingly the object of my invention to provide a system for sensing the temperature of a workpiece before each pass through the mill and adjust the screwdowns accordingly. As a result, the mill always operates at maximum efliciency and overloading is prevented.

In a preferred embodiment, the invention comprises temperature-sensing means on both sides of the mill and means for selectively rendering one of them effective, depending on the direction of the next succeeding pass. Also included are means for comparing the desired roll setting for the next pass with the existing roll setting and making the necessary adjustment. Finally, the system includes means for preserving until the next pass an indication of the setting of the mill for the last pass.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawing illustrating the present preferred embodiment. The single FIGURE of the drawing is a circuit diagram of the preferred control system.

Referring in detail to the drawing, a reversing mill has roller tables 11 and 12 on opposite sides thereof for handling a workpiece 13, such as an ingot, on its several passes forth and back through the mill. The mill has screws 14 for controlling the setting of the mill rolls, including a motor 15 under the control of a reversing panel 15a. Temperature measuring devices 16 and 16a are located above tables 11 and 12, respectively. A switch 16b is operated by the reversing mechanism of the mill, e.g., the main reversing controller, to connect a selected one of the temperature-measurement devices to a digital voltmeter 17. The temperature-measurement device on the side from which the piece next enters the mill is the one connected to the voltmeter. Devices 16 and 16a are bolometers such as made by Leeds and Northrup and shown in their catalog EN-S3. The voltmeter may be that described in catalog 356 of Non-linear Systems, Inc., Del Mar, California.

A stepping switch potentiometer 18 having equal resistance units connected between its fixed contacts is actuated by voltmeter 17 to apply a positive voltage to a differential amplifier 19, proportional to the temperature of ingot 13 on table 11, as observed by device 16. Amplifier 19 is of the type described in Wests Servomechanisms (English Universities Press, Ltd, London, 1953). It is subject also to an opposing voltage applied by a potentiometer 20, actuated in accordance with the setting of the rolls 10 at any given time. Amplifier 19 serves to cause operation of motor 15 to bring the mill screws to the position dictated by the position of potentiometer 18. When this condition prevails, amplifier 19 is balanced and its output is zero.

The setting of the mill for any given pass is established ice automatically as explained above, as soon as ingot 13 reaches table 11 and the mill is driven in the direction to roll from left to right as viewed in the drawing, the, final setting, of course, being dependent on the temperature of the ingot. After a proper setting of the rolls has been achieved for a given pass, an indication thereof must be preserved so that the proper voltage will be applied across the total resistance of potentiometer 18 to govern the adjustment necessary for the succeeding pass. For this purpose, I provide a digital voltmeter 21, similar to voltmeter 17, connected through a normally closed contact 22x of a manual reset switch 22, to potentiometer 20. A stepping-switch potentiometer 23 similar to potentiometer 18, controlled by voltmeter 21 varies the voltage applied to the resistance of potentiometer 18.

A lockout relay 24 is energized while the ingot is in the mill. Relay 24 may be controlled by a strain gage mounted on the mill housing or any other equivalent means such as a flag switch. At its back contact 24x, relay 24 opens the field circuit of motor 15 thus preventing any change in mill setting While a rolling pass is being performed. Relay 24 at its front contact 24a closes the circuit for operating coil 23a of potentiometer 23. The latter, therefore, steps to the proper position for the next pass while a given pass is proceeding. At the conclusion of a pass, relay 24 is deenergized to hold potentiometer 23 in the position in which it was stopped and to permit operation of motor 15.

On the next pass in (the opposite direction, a similar sequence of operations occurs, governed by temperaturemeasuring device 16a. When the rolling of the ingot has been finished, after the last pass from left to right, and the next ingot has reached table 11, reset switch 22 is manually operated and contacts 22a and 22b thereof apply voltage to coil 23a causing potentiometer 23 to advance clockwise to its last position. As a result, a fraction of the voltage across the resistor of switch 23 is applied to amplifier 19 by potentiometer 18, depending on the position to which it is advanced in response to the temperature of the next ingot. A further result is that amplifier 19 causes the roll pass to be opened to the maximum extent determined by a limit switch 25.

It will be evident that the invention provides a simple yet eifective system for causing the reduction in a rolling mill to proceed at the maximum rate permitted by the plasticity (temperature) of the workpiece, with due safeguard against overloading the mill.

Although I have disclosed herein the preferred embodiment of my invention, I intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the invention.

I claim:

1. A system for controlling the spacing between the rolls of a primary rolling mill according to the temperature of an ingot to be rolled therein comprising means adjacent the mill for sensing the temperature of an ingot before it enters the mill, means controlled by said sensing means establishing a voltage corresponding to said temperature, a potentiometer operated in accordance with the setting of the mill screws establishing a voltage corresponding to the roll spacing existing at the time, a differential amplifier subject to both said voltages and means for operating said screws controlled'by said amplifier.

2. A control system as defined in claim 1, characterized by a temperature-sensing means on each side of the mill and means actuated in accord with the direction in which the mill is driven for selectively connecting one of said temperature-sensing means in a control circuit.

3. A control system as defined in claim 1, characterized by said first-mentioned means being a bolometer positioned to receive radiation from said workpiece and said second-mentioned means including a digital voltmeter controlled by the bolometer and a stepping-switch potentiometer connected to said voltmeter V 4. A control system as defined in claim 1, characterized by adig'ital voltmeter, connectedito said potentiometer, and a stepping switeh potentiometer modifying said firstnientioned voltage.

] I References Citdin the file of this patent Stoltz n-. Apr. 28, 1942 4 Shayne et a1 Ian. 18, 1944 Whitten Oct. 24, 1944 Gille Feb. 14, 1956 Whalen Oct. 23, 1956 Peterson Apr. 8, 1958 FOREIGN PATENTS Germany Sept. 10, 1953 OTHER REFERENCES Process Programming' of Automatically Controlled Rolling Mills, Iron and Steel Engineer; pages 107-117,

July 1959. 

